1. Field of the Invention
The present invention relates to a controllable electrode device for intracardial stimulation of the heart of the type having an electrode cable containing an elongate, flexible conductor whose exterior is covered with a layer of insulation and whose interior forms a lumen for the introduction of a control element for bending the cable, and with an electrode head fitted at the conductor's distal end for stimulation of cardiac tissue.
2. Description of the Prior Art
It is of major importance for the electrode cable in an electrode device of the type described above to be pliant enough so it can, when introduced into the patient's heart via a vein, follow the course of the vein without damaging venous walls. In most instances, the electrode cable is introduced with the aid of a guidewire, inserted into the cable's lumen, made of a material having the stiffness still needed to advance the electrode cable through the vein. The stiffness of the electrode cable can thus be varied, depending on the guidewire's diameter and material. At difficult passages in which the electrode must bend considerably, the guidewire is often retracted a little so the distal end of the electrode cable has maximum pliancy. After passing such a passage, the guidewire is again pushed forward to the electrode cable's distal end (i.e., distal relative to a stimulation device to b3 connected at an opposite end) in order to advance this end into the atrium or ventricle of the heart until the electrode head bears against the heart wall for stimulation of the heart.
In U.S. Pat. No. 4,402,328, an electrode device of the above described type is disclosed having a J-shaped, precurved electrode cable whose electrode head is intended for insertion in the auricle of the atrium. When the electrode cable is introduced into the heart, the cable is straightened with a relatively stiff *stylet, which could cause complications in the passage of certain venous bends.
Another such electrode device is described in U.S. Pat. No. 4,136,703. In this electrode device, a relatively stiff tube, extending the length of the electrode cable, is inserted into the electrode cable's lumen. A J-shaped, precurved stylet, kept straight with the aid of the tube, is inserted into the tube. When the distal end of the cable is inside the heart, the tube is retracted, thereby exposing the stylet, which then shapes the distal end of the cable. An electrode cable of this kind is extremely stiff.